Winding of stationary induction apparatus

ABSTRACT

A disk winding of a stationary induction apparatus such as a power transformer or reactor in which, in order to improve the initial potential distribution due to intrusion of impulse voltage so as to distribute the potential substantially linearly over the entire length of the winding, the outer end of a shielding conductor incorporated in each coil section is connected solely with the outer end of a shielding conductor in the coil section which is spaced even-numbered layers of at least four layers from the first-mentioned coil section including the said coil section.

United States Patent Okuyama [451 Sept. 12, 1972 [5 WINDING OF STATIONARY 3,466,584 9/1969 Kashima ..336/70 INDUCTION APPARATUS 3,479,629 11/1969 Broszat ..336/84 X [72] Inventor: Kenichi Okuyama, Hitachi, Japan FOREIGN PATENTS OR APPLICATIONS 1 Assisnee= Himhi, y Japan 270,471 12/1964 Australia "336/70 22 i No 30 970 1,528,628 5/1970 France ..336/70 [21] Appl- No; 93,872 Primary Examiner-Thomas J. Kozma Rem Us. Application Du Attorney-Craig, Antonelli & Hill [63] Continuation of Ser. No. 829,982, June 3, [57] ABSTRACT 1 :3??? k gg fi ggy g A disk winding of a stationary induction apparatus such as a power transformer or reactor in which, in gfgg gg g I? a: fg g gz ggfg of order to improve the initial potential distribution due to intrusion of impulse voltage so as to distribute the potential substantially linearly over the entire length 35.8: of the winding, the outer end ofa shielding conductor [58] Fieid I69 70 84 incorporated in each coil section is connected solely with the outer end of a shielding conductor in the coil [56] References Cited section which is spaced even-numbered layers of at least four layers from the first-mentioned coil section including the said coil section.

6 Claims, 15 Drawing Figures PATENTEUSEP 12 72 3.691.494 sum 03 0F 10 FIG. 3 PRIOR ART I09 9 IO M I2 l3 l4 E] I6 06 402 o? 3 2o [Ea] as I? 403 I 1TH I I N VENTOR KENZLHI OKUY/IMA ATTORN E Y5 PATENTEDSEP 12 I912 3.691. 494

SHEET U l 0F 10 FIG. 4 PRIOR ART INV EN TOR KENZCHI K Y ATTORN E Y5 PATENTEDSEP 12 m2 SHEET OSUF 10 [NV ENT OR KENICHI OKLAYAMA Z mza v 240 ATTORNEYS PAIENTEDSEP 12 2 SHEET UBUF 10 w m m m m m a V F B w -W b WNW -d H. m m .a... T E; IETIM W FIEW; L m C 1 :I QEME EwE RmL N a 5 wdwflmwfixi 6 M W W in L m m M M T- h P n u "W" ll 2 A //////////A//////////// m 0 wd M INVENTOR KENICH-Z aKuyAMA ATTORNEYS PATENTEUSEP12 m2 SHEET over 10 INVENTOR KEA/lc/II OKM YAMA W 1 ATTORNEY PATENTEDSEP 12 m2 SHEET 080F10 9 l0 II FIG. ll

INVENTOR KE/VIC HZ oK YAMA A w awwd v Aw ATTORNEY) PATENTEDSEP 12 m2 3.691.494 SHEET DSOF 10 FIG. I2

INVENTOR KENICHI oKMYAMA WINDING OF STATIONARY INDUCTION APPARATUS CROSS-REFERENCES TO RELATED APPLICATIONS:

3,560,902, which is a continuation-in-part of application Ser. No. 326,845 filed Nov. 29, 1963, now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the invention This invention relates to a winding of stationary induction apparatus.

2. Description of the prior art:

In regard to stationary induction apparatus such as power transformers or reactors, it is common practice that the series capacity of the high-voltage winding thereof is made larger than the earth capacity of such winding in order to improve the impulse voltage characteristics of the winding. I

Generally, the high-voltage winding of a stationary induction apparatus of this kind is shaped in the form of a cylinder or disc. According to the former winding structure, it is not so difficult to maintain the series capacity of the winding at a predetermined value since individual layers forming the winding oppose to each other with a large area. However, the cylindrical winding described above is defective in that it is not so resistive to a mechanical force electromagnetically generated in the winding due to the combination of leakage flux and current flowing through the winding when an excessively large current caused by, for example, short-circuit flows into the winding.

In contrast with the cylindrical, winding structure, it is possible in the case of the disk winding structure to increase its strength against an electromagnetically generated mechanical force as described above. How ever, due to the fact that individual coil sections of the disk winding oppose to each other with a relatively small area and the number of the coil sections is so large, the disk winding has a small series capacity and thus its impulse voltage characteristics are quite unsatisfactory.

In an attempt to overcome, the above defects, various proposals have hitherto been made in order to improve the impulse voltage characteristics of the disk winding. Many of these proposals invariably involve electrostatically coupling the spaced coil sections to each other in such a manner that a charging current occurring due to intrusion of impulse voltage flows through one conductor of the coil section in a direction opposite to the direction of flow through the adjacent conductor or flows through the shielding conductor in the coil section in a direction opposite to the direction of flow through the coil conductor thereby canceling the inductance therebetween and providing a large series capacity between the coil sections.

In the interleaved winding representing one form of the prior art systems, a pair of adjacent coil sections are combined together to form a twin coil. In each twin coil, a conductor is wound .to form first an upper coil section and then alower coil section, the conductor led out of the lower coil into the space between the conductor portions of the upper coil section, and further the conductor led out of the upper coil section is guided into the space between the conductor portions of the lower coil section so that these cross each other in the twin coil. According to the interleaved winding described above, there are three connecting conductors between the coil sections in one twin coil, resulting in a complex coil structure which leads to an increase in time required for the manufacture of the coil. Further, the large number of the connecting conductors results in a large number of connections, which is undesirable electrically as well as mechanically since the weak point of the coil is thereby increased.

The inter-shielded winding which represents another form of the prior art windings includes warping a shielding conductor in each of a pair of adjacent coil sections and connecting the outer ends of the shielding conductors with each other between the adjacent coil sections. In the intershielded winding, it is difficult to obtain a sufficient series capacity between the coil conductor and the shielding conductor because the capacities between the two coil sections and the shielding conductor are connected in series with each other. Therefore, the potential distribution in the case of intrusion of impulse voltage into the winding can not sufficiently approach to the desired linearity.

The static shielded winding representing the third form of the prior art systems includes winding a shielding conductor into each coil section and connecting the outer end of the shielding conductor to the outer end of the coil conductor of the adjacent coil section thereby electrostatically coupling the adjacent coil sections to each other. According to the static shielded winding, the capacities between the coil conductors and the shielding conductors are connected in parallel with each other. Therefore, suppose that the number of turns of the shielding conductors is the same, then it is possible to obtain a series capacity which is twice as much as that in the case of the inter-shielding winding described above. In other words, the number of turns of the shielding conductor in the case of the static shielded winding may be half as large as that in the case of the inter-shielded winding to obtain the same series capacity.

By the way, the coil conductor in a winding of large capacity has a large cross-sectional area and an eddy current loss is developed in the winding due to crossing of leakage flux with the coil conductor. Common practice to reduce the eddy current loss includes bundling a required number of elementary conductors covered with a thin insulation, applying an insulating covering to the bundle to obtain a coil conductor consisting of many conductors, and forming a coil section from the coil conductor. However, in forming the coil from the many conductors, the elementary conductors must be transposed in the intermediate portion of the coil so as to thereby avoid generation of circulating current due to a difference in the number of lines of crossing leakage flux.

Generally, the respective elementary conductor are transposed at a portion where the outer end of one coil section is connected with the outer end of another coil section. When, therefore, the static shielded winding is applied to the coil section formed by winding a multiconductor of the kind described, the insulation covering of the coil conductor must be peeled off for effect ing a connection between the shielding conductor and the coil conductor. Such a connecting work must be performed on each coil section during the assembling of the winding, and a lot of time including the repair of insulation after connection is required for constructing the winding.

Especially, when the static shielded winding is applied to a continuous disk winding structure in which each coil section is formed from a continuous winding of a coil conductor, the insulation covering on the coil conductor must be peeled off once and then the necessary repair work must be performed. This cancels the advantage of the continuous disk winding structure which aims primarily at eliminating the necessity for the connecting work between the coil sections. When a transposed wire, in which a plurality of enameled elementary conductors are successively transposed and an insulation covering is applied to the bundle, is especially employed as the coil conductor, the enamel covering on each elementary conductor as well as the insulation covering on the bundle must be removed for effecting a connection between the shielding conductor and the coil conductor, and then the connected portion must be subjected to insulation repair work again, which consumes a lot of time and involves cost for the work.

SUMMARY OF THE INVENTION:

It is an object of the present invention to provide a winding of a stationary induction apparatus which is so arranged that the potential built up thereacross as a result of intrusion of impulse voltage thereinto can be distributed substantially linearly.

Another object of the present invention is to provide a winding of a stationary induction apparatus in which the series capacity between the coils is increased to attain the desired shielding effect without connecting the coil conductor with the shielding conductor incorporated in each coil section.

In order to constitute a disk winding from a plurality of first and second coil sections, the inner peripheral end of one of the first coil sections formed by winding a coil conductor from the outer periphery toward the inner periphery may be connected with the inner peripheral end of one of the second coil sections formed by winding a coil conductor from the inner periphery toward the outer periphery and which lies adjacent to one face of the first coil section described above, and the outer peripheral end of the said first coil section may be connected with the outer peripheral end of another second coil section which lies adjacent to the other face of the said first coil section, similar connections being successively provided between the remaining first and second coil sections. l-leretofore, it has been common practice to connect the outer peripheral ends of the coil sections with each other at the same position on the side of the circumference of the coilsections. Therefore, the shielding conductors must be connected with each other at a position beyond the connection between the outer peripheral ends of the first and second coil sections, and thus the outer diameter of the winding is inevitably increased.

It is therefore a further object of the present invention to provide a winding of a stationary induction apparatus in which the shielding conductors in the coil sections can be connected with each other without increasing the outside diameter of the winding.

In order to attain the above objects, the present invention provides a disk winding of a stationary induction apparatus including a plurality of first coil sections formed by winding a conductor by a plurality of turns from the outer periphery toward the inner periphery, and a plurality of second coil sections formed by winding a conductor by a plurality of turns from the inner periphery toward the outer periphery in the same direction as that of said first coil sections, in which the outer peripheral end of a first shielding conductor wound continuously between the turns of the coil conductor of each said first coil section is connected solely with the outer peripheral end of a second shielding conductor wound continuously between the turns of the coil conductor of the second coil sections which is spaced even-numbered layers of at least four layers from said first coil section including said first coil section.

According to such a shielding system, the shielding conductors may only be connected with each other and need not be connected with the coil conductors. It is therefore possible to reduce the number of connections in constituting the winding, thereby to minimize the connecting work and to manufacture the winding economically.

Further, according to the present invention, the shielding effect equivalent to or higher than the third shielding system described previously can be obtained without connecting the shielding conductor with the coil conductor so that the potential built up due to intrusion of impulse voltage can substantially uniformly be distributed over the entire length of the winding.

In the present invention in which the first shielding conductor wound between the turns of the coil conductor forming the first coil section is connected solely with thesecond shielding conductor wound between the turns of the coil conductor of the second coil section which is spaced more than four layers from the first coil section including the said first coil section, the number of skipped layers of the coil sections lying between the shielding conductors to be connected with each other may be largest in the coil sections disposed near a high-voltage line terminal and may continuously or stepwise decreased toward the coil sections disposed near an earth terminal. For example, in the coil sections disposed in the vicinity of the high-voltage line terminal, the first shielding conductor in the first coil section is connected with the second shielding conductor in the second coil section which is spaced eight or six layers from the first coil section including the said first coil section, while in the coil sections disposed in the vicinity of the earth terminal, the first shielding conductor in the first coil section is connected with the second shielding conductor in the second coil section which is spaced six or four layers from the first coil section including the said first coil section. By virtue of such a shielding system, the series capacity between the coils closer to the high-voltage line terminal where a most severe voltage distribution appears in the case of intrusion of impulse voltage can be made extremely large so that the voltage distribution in the winding can beimproved.

Further, in the present invention, the shielding conductor need not be incorporated in all of the coil sections ranging from the high-voltage line terminal to the earth terminal and the number of the coil sections incorporating therein the shielding conductor may suitably be selected depending on the voltage distribution appearing in the winding due to intrusion of impulse voltage. For the same reasons, the number of turns of the shielding conductor to be incorporated in the respective coil sections may suitably be determined.

According to the present invention, the connection connecting the outer peripheral ends of the coil sections may successively be displaced along the circumference of the winding so as to form a plurality of spaces which are successively circumferentially displaced along the outer periphery of the winding and these spaces may be utilized for connection between the shielding conductors. This arrangement is advantageous in that the outer peripheral portion of the winding does not bulge outwardly thereby increasing the outside diameter of the winding.

The shielding system according to the present invention is also applicable to a three-winding transformer equipped with a high-voltage winding, a medium-voltage winding and a low-voltage winding. Generally, the medium-voltage winding of a three-winding transformer is disposed between a low-voltage winding and a high-voltage winding. Thus, the earth capacity of the medium-voltage winding is larger than that of the highvoltage winding which is disposed most outside. It is therefore necessary that the medium-voltage winding has an especially large series capacity compared with that of the high-voltage winding. According to the present invention, the shielding conductors in the medium-voltage winding can be connected with each other by skipping a plurality of coil sections so as to provide a large series capacity between the coils.

Various problems encountered with prior windings and the features of the present invention will be described in detail hereunder so that the present invention can more clearly be understood.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic view showing the structure of a disk winding according to the interleaved winding.

FIG. 2 is a diagrammatic view showing the structure of a disk winding according to the inter-shielded windmg.

FIG. 3 is a diagrammatic view showing a prior art example of the structure of a disk winding accordingto the static shielded winding employing a single conduc- 01.

FIG. 4 is a diagrammatic view showing another prior art example of the structure of a disk winding according to the static shielded winding employing a double conductor.

FIG. 5 is a developed side view of part of the disk winding structure shown in FIG. 4 when looked from outside.

FIG. 6 is a partly sectional perspective view of a transposed wire.

FIG. 7 is a diagrammatic view showing the structure of a disk winding according to the present invention.

FIG. 8 is a plan view of the disk winding shown in FIG. 7.

FIG. 9 is a developed side view of part of one form of the disk winding shown in FIG. 7 when looked from outside.

FIG. 10 is a developed side view of part of another form of the disk winding shown in FIG. 7 when looked from outside.

FIG. 11 is a diagrammatic view showing the structure of another embodiment of the present invention.

FIG. 12 is a diagrammatic view showing the structure of a further embodiment of the present invention.

FIG. 13 is an equivalent circuit diagram for illustrating the state of distribution of capacities in the disk winding according to the present invention.

FIG. 14 is a'graphic illustration of the potential distribution in the disk winding of the present invention as compared with those of the disk windings according to the prior art shielding systems.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 through 5 show a few disk windings constructed in accordance with the prior art shielding systems described previously. In FIGS. 1 through 3, reference numeral designates the leg portion of an iron core of a stationary induction apparatus. Reference numeral 101 designates a layer of insulator surrounding the leg portion 100 of the iron core. When the stationary induction apparatus is a transformer, a low-voltage winding is disposed between the insulator layer 101 and the leg portion 100 of the iron core.

Referring to FIG. 1, a disk winding 200 comprising a plurality of coil sections 201, 202, 208, is disposed around the insulator layer 101. The odd-numbered coil sections or first coil sections, 201, 203, 205, 207, are formed by winding a coil conductor 102 by a plurality of turns from the outer periphery toward the inner periphery, while the even-numbered coil sections or second coil sections 202, 204, 206, 208, are formed by winding a coil conductor 102 by a plurality of turns from the inner periphery toward the outer periphery.'The uppermost coil section 201 of the first coil sections is connected with a high-voltage line terminal L. In the disk winding structure according to the interleaved shielding system shown in FIG. 1, the coil conductor of one coil section is interleaved between the coil conductor portions of the adjacent coil section in a manner that the former coil conductor crosses the latter coil conductor. Thus, in the case of, for example, the first coil section 201 and the second coil section 202, the coil conductor is wound in the order of Nos. 1, 2, 3 and 4 in the first coil section 201 and in the order of Nos. 5, 6, 7 and 8 in the second coil section 202. The coil conductor is then wound in the order of Nos. 9, l0, l1 and 12 between the coil conductor portions of the first coil section 201 and subsequently wound in the order of Nos. 13, 14, 15 and 16 between the coil conductor portions of the second 'coil section 202 thereby forming a pair of coil sections 201-202.

Therefore, in actual practice for the interleaved shielded winding, three connections a, b and c are required to connect the coil conductors 102 of each pair of coil sections. This is defective in that the coil structure becomes complex and the mechanical strength of the coil is lowered.

In the inter-shielded winding shown in FIG. 2, a disk winding 300 comprises a plurality of first coil sections 301, 303,v 305, and a plurality of second coil sections 302, 304, 306, A coil conductor 103 is continuously wound in a manner as shown to form each of the coil sections thereby to constitute a disk winding which is free from the defect described above. However, due to the fact that a shielding conductor 104 wound between the turns of the coil conductor 103 forming each of the first coil sections is connected by a connection d with a shielding conductor 105 wound between the turns of the coil conductor 103 of the adjacent second coil section, the series capacity between the first coil section 301 and the second coil section 302, between the first coil section 303 and the second coil section 304, and so on is only half as much as the series capacity distributed between each coil section and the shielding conductor.

In the static shielded winding shown in FIG. 3, a disk winding 400 comprises a plurality of first coil sections 401, 403, 405, and a plurality of second coil sections 402, 404, 406, A coil conductor 106 is continuously wound in a manner as shown to form each of the coil sections. A first shielding conductor 107 wound between the turns of the coil conductor 106 of the first coil section is connected by a connecting conductor 109 with the outer peripheral end of the coil conductor 106 of the adjacent second coil section, while a second shielding conductor 108 wound between the turns of the coil conductor 106 of the second coil section is likewise connected by a connecting conductor 109 with the outer peripheral end of the coil conductor 106 of the adjacent first coil section.

Therefore, according to the static shielding system described above, the series capacity between each coil section and the shielding conductor disposed therein is connected in parallel with the series capacity between each pair of the first and second coil sections, and thus the series capacity which is four times as much as that of the inter-shielded winding described above can be added. Thus, according to such static shielded winding, potential distribution in the winding upon intrusion of impulse voltage can be made substantially linear.

However, due to the fact that, in the static shielded winding, the shielding conductors 107 and 108 are connected with the outermost coil conductor portions of the adjacent coil sections, the insulation covering on the coil conductors must once be peeled off for making necessary connection at these portions and then the connections must be reinforced with electrical insulator again.

Especially when, as shown in FIG. 4, a discal winding 500 comprises a plurality of coil sections 501, 502, 508, which are formed from a multiconductor 110, elementary conductors 1 10a and 1 10b of the multiconductor 110 must be transposed at the bridging connection portion at the outermost layer of each coil section. At these transposed portions, first shielding conductors 111a, 111b, lllc, 111d, incorporated in the first coil sections 501, 503, 505, 507 must be connected by connecting conductors 113a, 113b, 113e, 113d, with second shielding conductors 112a, 112b, 112e, 112d, incorporated in the second coil sections 502, 504, 506, 508, respectively. This involves a complex winding work.

The disk winding structure shown in FIG. 4 will be described in more detail with reference to FIG. 5 which is a developed side view of part of the disk winding of FIG. 4.

In FIG. 5, inter-coil duct prices 114 are shown as radially disposed in a predetermined spaced relation between the coil sections. The pairs of adjacent first and second coil sections 501 and 502, 503 and 504, 505 and 506, 507 and 508, are connected with each other for connection between coils at similar positions on the line A-A along their outer periphery, and at the same time, the elementary conductors a and l10b of the coil conductor 110 are transposed at each of the connections between coils. On the other hand, the first shielding conductor 111 and the second shielding conductor I12 incorporated in the respective coil sections are alternately connected with the coil conductors of the adjacent coil sections on opposite sides of the connection between coils. For example, the outer peripheral end of the first shielding conductor 111a incorporated in the first coil section 501 is connected by the connecting conductor 113a with the elementary conductor 110a of the coil conductor 110 of the adjacent coil section 502 on the right-hand side of the connection between coils, while the outer peripheral end of the second shielding conductor 112a incorporated in the second coil section 502 is connected by the connecting conductor l13b with the coil conductor 110 of the adjacent coil section 501 on the left-hand side of the connection between coils. Similar connections are provided between the remaining shielding conductors and coil conductors.

It will be seen from the above description that, when the static shielded winding is applied to a disk winding structure consisting of a multiconductor, the connection between coils, i.e., the connection between each pair of coil sections protrudes outwardly in the radial direction of the coil and the connection between the shielding conductor and the associated coil conductor must be reinforced with electrical insulator with the result that the shape of the winding becomes oval in its plan view. This results in a defect that a large insulation distance is required between the casing of the electrical apparatus and the winding or between the windings of different phases, and the size of the electrical apparatus is correspondingly enlarged. While the connection between the coil sections is not especially required when a transposed wire 118 as shown in FIG. 6 is employed as the coil conductor in which a plurality of enameled wires 116a, 116b, l16n are transposed and are covered with an insulation covering 117. In such a case, however, the insulation covering 117 must be partly cut away and the enamel covering on each wire 116 must be peeled off to expose the conductor surface for providing electrical connection between the shielding conductor and the transposed wire 118. After completion of the connection between the shielding conductor and the transposed wire 118, the transposed wire 118 and the insulation covering 117 must be restored to their original state. Thus, application of the static shielded winding, which exhibits an excellent shielding effect, to a disk winding structure consisting of such a transposed wire 118 is extremely difficult in view of the complex work involved therein.

The present invention relates to a novel coil structure which is free from the defects encountered with the prior art shielding systems.

In accordance with the present invention, there is provided a highly reliable winding which can be manufactured with .a smaller amount of work than heretofore and in which any connection between a coil conductor and a shielding conductor as well as reinsulation of these conductors is not required. Further, in accordance with the present invention, there is provided a shielding system which is more effective than the prior art static shielded winding.

Referring to FIG. 7, the right-hand side of a disk winding 600 embodying the present invention is shown in section. Reference numerals 100 and 101 in FIG. 7 designate the leg portion of an iron core and a layer of insulator surrounding the leg portion 100 of the iron core, respectively. The disk winding 600 comprises a plurality of coil sections 601, 602, 608, and is disposed on the insulator layer 101. A coil conductor 1 19 forms each coil section and may be a multiconductor or transposed wire described previously. In the present embodiment, a transposed wire is employed to form each coil section and is illustrated as a single conductor for the sake of convenience. In the odd-numbered or first coil sections 601, 603, 605, 607, the coil conductor 119 is wound clockwise from the outer periphery toward the inner periphery, while in the even-numbered or second coil sections 602, 604, 606, 608, the coil conductor 119 is wound clockwise from the inner periphery toward the outer periphery.

The pairs of adjacent first and second coil sections are connected with each other at their inner peripheral ends by first connections 120a, 120b, 1206, 120d, while the pairs of adjacent second and first coil sections are connected with each other at their outer peripheral ends by second connections 1210, 121b, 121C, 121d, Thus, the coil conductor 1 I9 is wound in the order of Nos. 1 to 8 in the first coil section 601, in the order of Nos. 9 to 16 in the second coil section 602, in the order of Nos. 17 to 24 in the first coil section 603, in the order of Nos. 25 to 32 in the second coil section 604, and so on. A required number of these coil sections 601, 602, 608, are stacked in tiers to constitute the disk winding 600. The outer peripheral end of the uppermost coil section 601 is connected by a connection 121L with a high-voltage line terminal L.

FIG. 8 is a plan view of such a winding structure.

FIG. 9 is a developed side view of part of the winding shown in FIG. 7 to illustrate the state of connection between the coil sections and the state of connection between shielding conductors described later. Symbols 0,, 0 0 and 0, 0 in FIG. 9 show corresponding positions of like symbols shown in FIG. 8. I Since, in the present embodiment, a transposed wire is employed to form each coil section as described above, the coil conductor 119 is not cut off in its intermediate portion and thus the entire winding can continuously be formed on the insulator layer 101 by a known winding work. In this case, the connections between coils 1210, 121b, 1210, 121d, disposed at the outer periphery of the coil sections are wound by a number of turns which is slightly less than a certain integer as seen in FIG. 9 unlike the case of the prior art system shown in FIG. 5 and shift to the next adjacent coil sections at these portions.

In the illustrated embodiment, the circumference of the coil section is equally divided into 20 parts so that the shift to the next adjacent coil section is effected with an angular difference of one-twentieth. Thus, in this embodiment, the angle of shift is 360 1/20 18. Where the outside diameter of the coil section is small, the angle of shift is desirably larger than 18, while where the outside diameter of the coil section is large, the angle of shift may be smaller than 18. Thus, the angle of shift may suitably be selected in relation to the outside diameter of the coil section. It will be understood that, by successively displacing the position of the connection between coils at the outer periphered end of the coil section by a predetermined angle, the starting and terminating ends of one coil section are displaced from those ends of the adjacent coil section to provide a space in the radial direction of the coil which space is useful for connection between shielding conductors described below.

In the respective odd-numbered or first coil sections 601, 603, 605, 607, shielding conductors 122a, 122b, 1226, are wound together with the coil conductor 119, while in the respective even-numbered or second coil sections602, 604, 606, 608, shielding conductors 123a, 123b, 1230, are wound together with the coil conductor 119. The structure of the winding in this respect is similar to the prior art system shown in FIGS. 3 and 4. The inner peripheral end of the shielding conductor is reinforced with insulator and opens in the associated coil section. The number of turns of the shielding conductor is so selected as to give a necessary capacity which is determined by calculation in the course of design of the winding. The number of turns of the shielding conductor is not necessarily fixed over all of the coil sections 601, 602, 608, The number of turns may be largest in the vicinity of the high-voltage line terminal L and may be successively decreased toward the neutral terminal. Further, the amount of insulation covering on the coil conductor 119 and on the shielding conductors 122a, 122b, 123a, 123b, may suitably be regulated from coil to coil depending on the voltage which is expected to generate. Since the sole function of the shielding conductor is to allow a flow of charging current therethrough, the shielding conductor is not necessarily of copper or aluminum but may be a conductor having a conductive surface coating of paint or the like.

The first shielding conductor 122a in the first coil section 601 located in the first layer is connected by a connection 124a with the second shielding conductor 123b in the second coil section 604 located in the fourth layer, while the first shielding conductor 122b in the first coil section 603 located in the third layer is connected by a connection 124): with the second shielding conductor 1230 in the second coil section 606 located in the sixth layer. Similarly, the first shielding conductor in any one of the remaining first coil sections is connected with the second shielding conductor in the second coil section which lies in the fourth layer from the said first coil section, except that the second shielding conductor 123a in the second coil section 602 located in the second layer is connected by a connection 124 with the input terminal L of the winding and the shielding conductor in the last layer is connected with the other terminal of the winding.

This manner of connection has been difficult to attain with the prior art coil structure shown in FIGS. 3 and 4. This is because, in the prior art winding structure shown in FIGS. 4 and 5, the connections between coils 1 a and l10b between the first coil section in the oddnumbered layer with the second coil section in the even-numbered layer are generally disposed on a straight line which is parallel with the axis of the coil. Because of such arrangement, an attempt to connect, for example, the shielding conductor 111a with the shielding conductor 1l2b results in crossover of those portions of the shielding conductors which come out of the turns of the coil sections.

In order to avoid such trouble with the prior art coil structure, an additional turn of one of the first and second shielding conductors must be provided on the outer peripheral face of the coil conductor. However, the height of the shielding conductor must be lower than that of the coil conductor in order to firmly mechanically hold the coil in place. Therefore, winding the shielding conductor over an excessively long distance results in difficulty of holding the shielding conductor in place and in an increase in the coil dimensions. In addition to the above defects, the shielding effect would be reduced tohalf since this shielding conductor portion is in contact with the coil conductor only with its one side face.

The above defects can be overcome by the arrangement shown in FIG. 9 which is a developed view of the embodiment of the present invention. In the present invention, the connection between the coil sections has a turn which is slightly less than an integer, and thus the shielding conductors 122a and 123b can easily be connected with each other at a position outside of the coil conductors. In this case, the connections 124a, 124b, extending over the surface of the coil conductors have a very short length and thus it is almost unnecessary to secure the shielding conductors in place. After the respective coil sections are continuously wound to form the winding which is free from any intermediate connections, the shielding conductors are connected with each other by soldering or welding and then electrical insulation is applied to the shielding conductors. The disk winding formed by the method of winding and by the method of connecting the shielding conductors described above is continuous throughout the entire length thereof which is substantially limited by the length of wire that can be manufactured.

In the arrangement shown in FIG. 9, the connection 124a between the first shielding conductor 122a incorporated in the first coil section 601 and the second shielding conductor 123b incorporated in the second coil section 604 is situated on the left-hand side of the outer connection 121a between the second coil section 602 and the first coil section 603. Further, the connection 124b between the first shielding conductor 122b incorporated in the first coil section 603 and the second shielding conductor 1230 incorporated in the second coil section 606 is situated on the right-hand side of the outer connection 121b between the second coil section 604 and the first coil section 605.

However, in accordance with the present invention, the positions of the connections 124a and 124b and similar connections may be reversed as shown in FIG. 10.

Referring to FIG. 11 showing another embodiment of the present invention, a disk winding 700 comprises a plurality of odd-numbered on first coil sections 701, 703, 705, formed by winding a coil conductor and a plurality of even-numbered or second coil sections 702, 704, 706, formed by winding a coil conductor 125. First shielding conductors 126a, 126b, 1266, are incorporated in the respective first coil sections 701, 703, 705, while second shielding conductors 127a, 127b, 127e, are incorporated in the respective second coil sections 702, 704, 706, In this embodiment, the first shielding conductors are connected with the second shielding conductors by third connections 128a, 128b, 128e, in such a manner that the first shielding conductor in one of the first coil sections is connected with the second shielding conductor in the second coil section which lies in the sixth layer from the said first coil section. More precisely, the first shielding conductor 126a incorporated in the first coil section 701 is connected by the third connection 128a with the second shielding conductor 127c incorporated in the second coil section 706 which lies in the sixth layer from the first coil section 701, while the first shielding conductor 126b incorporated in the first coil section 703 is connected by the third connection l28b with the second shielding conductor 127d incorporated in the second coil section 708 which lies in the sixth layer from the first coil section 703. The connection between the related shielding conductors is completed in this manner. The second shielding conductors 127a and 127b incorporated in the second coil sections 702 and 704 are connected through fourth connections 128, 128" and 128 with a high-voltage line terminal L, respectively. According to the embodiment shown in FIG. 11 having such an arrangement, a larger potential difference can be provided between the coil conductor and the shielding conductor in each coil section thereby to further increase the series capacity.

FIG. 12 shows an improvement of the embodiment shown in FIG. 11. Referring to FIG. 12, a disk winding 800 comprises a plurality of first coil sections 801, 803, 805, formed by winding a coil conductor 129 and a plurality of second coil sections 802, 804, 806, formed by winding a coil conductor 129. First shielding conductors 130a, 130b, 1306, are wound by a plurality of turns in the respective first coil sections 801, 803, 805, while second shielding conductors 131a, 131b, 1310, are wound by a plurality of turns in the respective second coil sections 802, 804, 806, In the present embodiment, the first shielding conductors are connected with the second shielding conductors by third connections 132a, 132b, 132e, in such a manner that the first shielding conductor in one of the first coil sections is connected with the second shielding conductor in the second coil section which lies in the eighth layer from the said first coil section. The second shielding conductors 131a, 131b, and 131C in the second coil sections 802, 804 and 806 disposed near the high-voltage line terminal L are connected with the high-voltage line terminal L through fourth connections 132', 132", 132" and 132, respectively. According to the embodiment shown in P16. 12, a much larger series capacity can be obtained.

ments shown in FIGS. 11 and 12 are advantageous in this respect.

Although not shown herein, the shielding in the vicinity of the high-voltage line terminal may have a large number of skipped layers of coil sections as shown in FIG. 11 or 12 and the shielding in the vicinity of the neutral terminal may have a form as shown in FIG. 7 or may be the prior art inter shielded winding in order that the series capacities of the coil are successively reduced from the high-voltage line terminal toward the neutral terminal. Further, a series capacity most suitable for each coil section can be provided by varying the number of skipped layers of coil sections in the manner described above and successively reducing the number of turns of shielding conductor in the coil sections.

The fact that the disk winding according to the present invention exhibits an effect electrically entirely the same as that of the prior art static shielded winding shown in FIG. 3 will be described with reference to FIG. 13.

FIG. 13 is an equivalent circuit diagram of FIG. 7. The potential difference between the coil conductor 119 of the coil section 601 and the shielding conductor 122a adjacent to the coil conductor 119 is equal throughout the coil section 601 since the shielding conductor and the coil conductor are wound around the iron core in parallelly adjacent relation to each other. Thus, the capacity therebetween is generally indicated by K. Likewise, the same capacity K exists between the coil section 602 and the shielding conductor 123a, between the coil section 603 and the shielding conductor 122b, between the coil section 604 and the shielding conductor 123b, and so on. Suppose that a potential difference V exists between the coil section 601 and the coil section 604. Then, it is apparent that the potential at the connection 124a between the shielding conductor 122a and the shielding conductor 12312 is Vr V/2 since the shielding conductors 122a and 123b are electrostatically coupled to the respective coil sections 601 and 604. On the other hand, it is also apparent that the potential at the connection 121a between the coil section 602 and the coil section 603 is Vx V/2. Therefore, connection between the points X and Y, that is, connection between the shielding conductor and the coil conductor is substantially unnecessary although such a connection is necessary in the case of the prior art structure shown in FIG. 3. Thus, the effect of the shielding system according to the present invention is entirely the same as that exhibited by the prior art shielding system.

The above fact was clearly verified by an experiment whose results are shown in FIG. 14. The experiment was performed on the high-voltage winding of a twowinding transformer rated at single phase, 20 MVA, 154/ /3/ll KV. The coil sections of the highvoltage winding under test have ten turns in the vicinity of the high-voltage terminal L and I6 turns in the vicinity of the neutral terminal. The shielding conductors have four turns in the vicinity of the high-voltage terminal L and zero turn in the vicinity of the neutral terminal. These coil sections and shielding conductors constitute together with insulation coverings a disk winding wherein the coil sections have the same outside diameter.

In FIG. 14, the horizontal axis indicates the coil length l in per cent and the vertical axis indicates the maximum voltage E in per cent generated in the coil relative to the terminal L to which a test voltage is applied. The curve (a) in FIG. 14 represents the characteristic obtained when no shielding conductor is provided, the curve (b) the characteristic obtained when shielding conductors are provided and connected in accordance with the inter shielded winding'shown in FIG. 2, the curve (0) the characteristic obtained when shielding conductors are connected in accordance with the prior art static shielded winding shown in FIG. 3, the curve ((1) the characteristic obtained when shielding conductors are connected in accordance with one form of the system of the present invention shown in FIG. 7, and the curve (g) the ideal characteristic which should be obtained when voltage is distributed uniformly across the coil section. The inter shielded winding shown in FIG. 2 is apparently inferior to the static shielded winding shown in FIGS. 3 and 4 even when the number of turns of the shielding conductors in the former is the same as the number of turns of the shielding conductors in the latter. As expected already, the system according to the present invention exhibited a characteristic substantially the same as that exhibited by the prior art static shielded winding.

The curves (e) and (f) in FIG. 14 represent the characteristics of other forms of the present invention. More precisely, the curve (e) represents the characteristic obtained with the shielding system shown in FIG. 11 in which the shielding conductor in any one of the first coil sections is connected with the shielding conductor in the second coil section which lies in the sixth layer from the former coil section. The curve (f) represents the characteristic obtained with the shielding system shown in FIG. 12 in which the shielding conductor in any one of the first coil sections is connected with the shielding conductor in the second coil section which lies in the eighth layer from the former coil section. It will be seen that the impulse voltage characteristics can be improved with an increase in the number of skipped coil sections. It will be seen further that the coil structure according to the present invention can easily be obtained when the shielding conductors are connected with each other in a manner as shownin FIG. 9 or 10.

It will be appreciated from the foregoing description that the present invention is advantageous over the prior art static shielded winding and any other systems in that the time required for the connection and re-insulation of coil conductors can be shortened, the winding so obtained is almost free from connection and has a high reliability electrically as well as mechanically, and the winding is sufficient resistive to impulse voltage.

I claim:

1. A winding of a stationary induction apparatus comprising a plurality of first coil sections formed by winding a conductor by a number of turns less than a predetermined integer from the outer periphery toward the inner periphery, a plurality of second coil sections formed by winding a conductor by a number of turns less than a predetermined integer from the inner periphery towards the outer periphery in the same direction as that of said first coil sections, a first connection connecting the inner end of each first coil section with the inner end of the second coil section which lies adjacent to one face of said first coil section, a second connection connecting the outer end of each first coil section with the outer end of the second coil section which lies adjacent to the other face of said first coil section in such a relation that one of said second connections is displaced a predetermined angle from another second connection in the circumferential direction of said coil sections, a first shielding conductor continuously wound between the conductor turns of each first coil section and having its inner end opened in said coil section, a second shielding conductor continuously wound between the conductor turns of each second coil section and having its inner end opened in said coil section, a third connection connecting solely the outer end of the first shielding conductor in each first coil section with the outer end of the second shielding conductor in the second coil section which is spaced by an even-number of layers of at least four layers from said first coil section including said first coil section in such a relation that said third connection is successively displaced in the circumferential direction of said coil sections, and a fourth connection connecting the shielding conductor in the second coil section disposed near a high-voltage line terminal with said high-voltage line terminal.

2. A winding of a stationary induction apparatus as claimed in claim 1, in which said third connection is provided between the outer end of the first shielding conductor in each said first coil section and the outer end of the second shielding conductor in the second coil section which is spaced four layers from said first coil section including said first coil section.

3. A winding of a stationary induction apparatus as claimed in claim 1, in which said third connection is provided between the outer end of the first shielding conductor in each said first coil section and the outer end of the second shielding conductor in the second coil section which is spaced six layers from said first coil section including said first coil section.

4. A winding of a stationary induction apparatus as claimed in claim 1, in which said third connection is provided between the outer end of the first shielding conductor in each said first coil section and the outer end of the second shielding conductor in the second coil section which is spaced eight layers from said first coil section including said first coil section.

5. A winding of a stationary induction apparatus as claimed in in claim 1, in which the conductor forming said first and second coil sections is a transposed wire.

6. A winding of a stationary induction apparatus as claimed in claim 1, in which said first and second shielding conductors are continuously wound by a plurality of turns between the conductor turns of said first and second coil sections, respectively. 

1. A winding of a stationary induction apparatus comprising a plurality of first coil sections formed by winding a conductor by a number of turns less than a predetermined integer from the outer periphery toward the inner periphery, a plurality of second coil sections formed by winding a conductor by a number of turns less than a predetermined integer from the inner periphery towards the outer periphery in the same direction as that of said first coil sections, a first connection connecting the inner end of each first coil section with the inner end of the second coil section which lies adjacent to one face of said first coil section, a second connection connecting the outer end of each first coil section with the outer end of the second coil section which lies adjacent to the other face of said first coil section in such a relation that one of said second connections is displaced a predetermined angle from another second connection in the circumferential direction of said coil sections, a first shielding conductor continuously wound between the conductor turns of each first coil section and having its inner end opened in said coil section, a second shielding conductor continuously wound between the conductor turns of each second coil section and having its inner end opened in said coil section, a third connection connecting solely the outer end of the first shielding conductor in each first coil section with the outer end of the second shielding conductor in the second coil section which is spaced by an even-number of layers of at least four layers from said first coil section including said first coil section in such a relation that said third connection is successively displaced in the circumferential direction of said coil sections, and a fourth connection connecting the shielding conductor in the second coil section disposed near a high-voltage line terminal with said high-voltage line terminal.
 2. A winding of a stationary induction apparatus as claimed in claim 1, in which said third connection is provided between the outer end of the first shielding conductor in each said first coil section and the outer end of the second shielding conductor in the second coil section which is spaced four layers from said first coil section including said first coil section.
 3. A winding of a stationary induction apparatus as claimed in claim 1, in which said third connection is provided between the outer end of the first shielding conductor in each said first coil section and the outer end of the second shielding conductor in the second coil section which is spaced six layers from said first coil section including said first coil section.
 4. A winding of a stationary induction apparatus as claimed in claim 1, in which said third connection is provided between the outer end of the first shielding conductor in each said first coil section and the outer end of the second shielding conductor in the second coil section which is spaced eigHt layers from said first coil section including said first coil section.
 5. A winding of a stationary induction apparatus as claimed in in claim 1, in which the conductor forming said first and second coil sections is a transposed wire.
 6. A winding of a stationary induction apparatus as claimed in claim 1, in which said first and second shielding conductors are continuously wound by a plurality of turns between the conductor turns of said first and second coil sections, respectively. 